1. Field of the Invention
The present invention relates to an ornithopter, and more specifically, to a power-driven ornithopter using an electric motor as a power source.
2. Description of the Prior Art
An ornithopter that mimics flight of an insect or bird corresponds to a very primitive model but has been hardly put to practical use. An aircraft model that has been put to practical use is largely divided only into a fixed wing aircraft and a rotary wing aircraft. The reason why the ornithopter has not been put to practical use is that analyses of a lift and a thrust to be generated by flapping of its main wings is very complicated as compared with those of the fixed wing aircraft and the rotary wing aircraft, and thus, it is difficult to design an ornithopter model ensuring a flight stability in view of flight dynamics and it is complex to design an actuating mechanism for performing the flapping.
However, the ornithopter still arouses persons"" curiosities due to its nature-friendly shape. There have been continuous attempts to develop the ornithopter as a leisure or toy aircraft that requires a relatively lower flight stability.
Recent attempts to develop the ornithopter will be described below.
U.S. Pat. No. 4,729,748 (Mar. 8, 1988) issued to Gerard Van Ruymbeke discloses a flying toy. The flying toy includes a body, main wings and tail wings that have appearances similar to those of a body, wings and a tail of a bird; an elastic band; a wind-up assembly for twisting the elastic band; an activation assembly for activating flapping of the main wings, which is similar to flapping of the wing of the bird, by transferring force released when the twisted elastic band is untwisted; and a latching assembly for latching or locking the main wings when the elastic band is twisted. U.S. Pat. No. 5,163,861 (Nov. 17, 1992) issued to Gerard Van Ruymbeke discloses a wing-operated flying toy and a process for automatically locking the wings at the end of a flight. The flying toy of the ""861 patent is constructed such that a locking device, which is similar to the latching assembly of the toy of the ""748 patent, locks the main wings even when the toy is flown while the elastic band is untwisted.
U.S. Pat. No. 4,749,149 (Jul. 7, 1988) issued to Peter Gruich discloses an ornithopter-type vehicle and methods of constructing and utilizing the same. The ornithopter-type vehicle is designed as an aircraft which is large enough to load persons thereinto. The ornithopter-type vehicle has main wings and a horizontal tail attached to its body in a manner similar to the fixed wing aircraft. An up motion of the flapping of the main wings that move between their higher and lower positions is established by elastic restoring force. A down motion of the flapping is established by power transferred from a power source through a hydraulic circuit. The ornithopter-type vehicle simultaneously obtains both the lift and thrust by the down motion of the main wings in a downward and rearward direction rather than a vertically downward direction from the higher position. The ornithopter-type vehicle is constructed such that its flight attitude is maintained in such a manner that a user controls the motion of the main wings and the position of the horizontal tail through operating levers.
U.S. Pat. No. 5,899,408 (May 4, 1999) issued to Kenneth R. Bowers, Jr. discloses an ornithopter. The ornithopter also has a main wing and a horizontal tail attached to its body in a manner similar to the fixed wing aircraft and employs a gasoline engine as a power source. The ornithopter is provided with flaps formed at the bottoms of the main wing so as to increase the lift obtainable from the flapping of the main wing.
As described in the aforementioned ""408 patent, the reason why the ornithopter has not been yet put to practical use regardless of whether it is a toy ornithopter or a manned ornithopter is that the lift obtainable from the flapping of the main wings is small and an activating mechanism and a power source capable of generating the flapping of the main wings cannot provide sufficient power and are too complicated and heavy.
The present invention is conceived to solve the problems in the prior art. An object of the present invention is to provide an ornithopter with an airframe structure that is lightweight, simple and stable and can generate sufficient lift and thrust.
Another object of the present invention is to provide an ornithopter having a lightweight, simple and durable power transmission mechanism and a simply-operable power source capable of ensuring longer flight time with respect to its weight.
An ornithopter according to the present invention for achieving the objects comprises a body, a main wing attached to an upper portion of a front section of the body, and a tail wing attached to a rear section of the body. A power source and a power transmission mechanism are installed within a housing of the body. The main wing includes a wing frame composed of a plurality of frame rods, and a skin attached to the wing frame for forming an outline of the main wing. The wing frame of the main wing is supported by a support means that is exposed to the outside at the upper portion of the front section of the body. The power transmission mechanism includes a gear train for adjusting the rotational motion of the electric motor at a proper speed and transferring it to the main wing, and connecting rods for converting the rotational motion into a swing motion of the main wing.
Preferably, the body includes a keel, which is made of a lightweight and rigid unitary panel, for supporting components contained in the body. The housing for enclosing the keel and the contained components is composed of two members, left and right halves.
The housing of the body is preferably constructed such that an extra space is formed between a front end of the housing and a front end of the power transmission mechanism to extend from the front end of an electric motor and the power transmission mechanism, which are mounted at a front end of the keel panel, to a position forward spaced apart therefrom. It is preferred that the extra space be filled with a shock absorbing material.
Preferably, each front frame rod extends along a front edge of the main wing from a position near a central axis of the body to a tip of the main wing and is initially formed in the shape of a straight line. Each rear frame rod extends from a position near an intersection of the central axis of the body and a rear edge of the main wing, and is connected to the front frame rod near an end of the tip of the main wing, i.e. a distal end of the front frame rod. Respective traverse frame rods extend from the front frame rod to the rear edge of the main wing.
Herein, if it is not specifically described, it should be understood that all the terms for designating the directions are used to refer to directions based on the ground in a state where the ornithopter according to the present invention is placed on the ground with a normal attitude.